Flight Tribhuvan International Airport departs from Kathmandu Tribhuvan International Airport at 00:25 and arrives at Bangkok Suvarnabhumi Airport at 05:10.
The flighttime is about 3h 45m. The distance travelled ("as the bird flies"): 1701 Km. So the average speed is roughly 454 Km.
There is an 1 hour time difference between Kathmandu and Bangkok